1. Field of the Invention
The present invention relates to a checking method of a wiring harness arranged in a mobile unit such as a motor vehicle.
2. Related Art
A motor vehicle has a wiring harness for supplying power to electrical appliances such as various lamps and motors from a battery. A conventional wiring harness includes a plurality of electrical cables, a plurality of terminals each fitted to an end of each electrical cable, connector housings accommodating the terminals, etc.
An ordinary or high grade car has an increasing number of on-vehicle electronics components, which requires hundreds to thousands of electrical cables. Thus, a wiring harness for such a car tends to have an increasing number of electrical cables.
A plurality of sub-harnesses are pre-assembled and each wiring harness is obtained by assembling the sub-harnesses. The sub-harness has a plurality of electrical cables, terminals each connected to an end of the electrical cable, and a connector housing accommodating some of the terminals. The sub-harness may have terminals which are not received in the connector housing to be an unprotected state.
An electrical continuity check of the wiring harness will be carried out after combination of the sub-harnesses when the sub-harnesses has the unprotected terminals, due to the circuit incompleteness of the sub-harnesses. In the electrical continuity check of the wiring harness, the terminals each are checked in electrical continuity with the other terminals to determine acceptance or rejection of the wiring harness. Such checking methods of the wiring harness have been carried out through the following sequential steps.
Each terminal of the wiring harness is selected sequentially to supply a voltage, while the other terminals of the wiring harness are checked in voltage thereof. Thereby, the electrical continuity relationship of the terminals can be known.
The obtained electrical continuity relationship of the terminals is compared with a pre-designed electrical continuity pattern of the wiring harness. Thereby, acceptance or rejection of the wiring harness has been determined, and an incorrect continuity point of the wiring harness could be found, if present.
The aforementioned conventional checking method of the wiring harness applies a voltage to each terminal sequentially to measure the other terminals in voltage. Thus, the voltage application is repeated for the total number of the terminals, so that it disadvantageously takes a long time to check the wiring harness since the electrical cables and terminals are increasing in number.
For example, it takes a time T that a voltage is applied to one of the terminals of the wiring harness to measure the other terminals in voltage. When the wiring harness has 3,000 terminals, it requires a time of Txc3x973,000 for checking electrical continuity of the terminals.
Moreover, it is necessary to transfer the wiring harness from its production line to a checking apparatus. Thereby, a long time is required to complete the wiring harness, causing a decreased productivity of the wiring harness.
In addition, it is difficult to know which assembling step of the wiring harness has been incorrect, since the electrical continuity of the terminals is checked after the completion of the wiring harness.
Furthermore, when an incorrect continuity point of a wiring harness is recognized, another wiring harness or an intermediate product which includes the same incorrectness would have been assembled. This tends to cause a further decreased productivity of the wiring harnesses.
Therefore, an object of the invention is to provide a checking method of a wiring harness, in which an appropriate productivity of the wiring harness is achieved.
For achieving the object, a checking method according to the present invention is provided for determining acceptance or rejection of a wiring harness having a plurality of first sub-harnesses and a plurality of second sub-harnesses. The first sub-harnesses has a plurality of electrical cables, a plurality of first press-fit terminals, and a first isolator. The first press-fit terminal is joined to each end of the first electrical cable. The first isolator holds the first press-fit terminals positioned at one end of the first sub-harness. The second sub-harness has a plurality of second electrical cables, a plurality of second press-fit terminals, a plurality of crimp terminals, a connector housing for accommodating the crimp terminals, and a second isolator supporting the second press-fit terminals. The second press-fit terminal is connected to one end of the second electrical cable. The crimp terminal is connected to the other end of the second electrical cable. When any of the first and second isolators are layered, the press-fit terminals held by different ones of the isolators can be connected to one another. The method includes:
a first decision step for determining acceptance or rejection of the first sub-harness after assembling of the first sub-harness,
a second decision step for determining acceptance or rejection of the second sub-harness after assembling of the second sub-harness, and
a third decision step for determining acceptance or rejection of the wiring harness after layering the isolators of the first and second sub-harnesses to complete the wiring harness.
a first decision step for determining acceptance or rejection of the first sub-harness after assembling of the first sub-harness,
a second decision step for determining acceptance or rejection of the second sub-harness after assembling of the second sub-harness, and
a third decision step for determining acceptance or rejection of the wiring harness after layering the isolators of the first and second sub-harnesses to complete the wiring harness.
Preferably, the third decision step inspects electrical continuity between the press-fit terminals of the layered isolators.
Preferably, the first decision step inspects electrical continuity between the press-fit terminals constituting the first sub-harness.
Preferably, the second decision step inspects electrical continuity between the terminals constituting the second sub-harness.
Further preferably, the first press-fit terminal has a press-fit portion for press-fitting the first electrical cable on the terminal and a crimping piece for crimping the first electrical cable to the terminal, and a press-fitting machine press-fits the first electrical cable to the press-fit portion of the first press-fit terminal and the press-fitting machine crimps the first electrical cable to the crimping piece. The press-fitting machine has a plurality of press-fitting means with an electrical conductivity. The first decision step inspects electrical continuity between the press fit means each of which contacting the crimping piece when the first electrical cable is press-fitted to the first press-fit terminal.
According to the main aspect of the invention, the first decision step determines acceptance or rejection of the first sub-harness, and the second decision step determines acceptance or rejection of the second sub-harness. Thus, the sub-harnesses are checked one after another just after the assembling thereof, eliminating the production of a plurality of sub-harnesses having the same incorrectness of a short circuit or an open circuit.
The first or second decision step determines acceptance or rejection of the first or second sub-harness. Such incorrectness can be quickly found to be repaired, improving a productivity of the wiring harness.
Moreover, the sub-wiring harnesses are checked one after another so that the production of a type of sub-wiring harnesses, in which an incorrectness have been found, is stopped. This prevents an otherwise decreased productivity of the wiring harness.
According to one of the preferable aspects of the present invention, after completion of the wiring harness, it is only required that the predetermined press-fit terminals are checked in electrical continuity therebetween. This decreases a total checking time of the wiring harness.
The electrical continuity condition between the press-fit terminals mounted on the different isolators is checked, allowing a decreased check time of the wiring harness. Thus, in addition, the wiring harness can be checked when it is in the production line for combining the sub-harnesses. Accordingly, the wiring harness requires no transfer from the wiring harness assembling line to another specified check apparatus, allowing an improved productivity of the wiring harness.
According to another of the preferable aspects of the invention, during an assembling step of the first sub-harness for fitting the first electrical cable to the first press-fit terminal, the electrical continuity between the press-fit means contacting the press-fit terminals is checked. This enables to surely find an incorrect closed or open circuit of the first sub-harness.
The electrical continuity between the press-fit terminals constituting the first sub-harness is checked, allowing to surely find incorrectness of a short circuit or an open circuit of sub-harness. Such incorrectness can be quickly found, improving a productivity of the wiring harness. Furthermore, the electrical continuity check of the first electrical cable is carried out during a fitting work of the first press-fit terminal, allowing a further improved workability.